Texture stretched, polka dots
I agree with the commenters, but I will go ahead and further explain what goes on here.
A UV map is instructions for how to take an image, and wrap it onto a mesh like wrapping paper. The problem you are having is probably because one of these: UV maps (quite justifiably) do not care about

Different aspect ratios of the image than that expected.
Changes in the scale of the mesh (this is a very good thing, but is likely the trouble you are having).

What is the scale of your object?
How did you make your UV map?
Did you scale the mesh within edit mode after you had UV unwrapped it?

... Find out next time on The Happy Family!